Modulation of cytokine and beta-defensin 2 expressions in human gingival fibroblasts infected with Chlamydia pneumoniae

Abstract

Human beta-defensin 2 is an antimicrobial peptide that is produced by several epithelial cells after stimulation with micro-organisms and inflammatory mediators. Gram-negative bacteria, which are typically detected in periodontal pockets in periodontitis, elicit a stronger antibacterial peptide response of human beta-defensin 2 by epithelial cells. In this study, we investigated whether Chlamydia pneumoniae is able both to enter and grow in human gingival fibroblasts (HGF), to modify the production of cytokines, and is involved in regulation of beta-defensin 2 expression. Gingival fibroblasts discarded from periodontal procedures on healthy young individuals were infected with viable C. pneumoniae or with heat- or ultraviolet-inactivated organisms at a multiplicity of infection of 4 inclusion-forming units per cell. Our results demonstrate that after 48 h of incubation with viable C. pneumoniae, gingival fibroblasts showed a proliferative response as seen by both colorimetric assay and direct cell count (40% and 45%, respectively). Moreover, cells incubated with viable or ultraviolet light-inactivated C. pneumoniae organisms showed an increase in the levels of interleukin-6, interleukin-10 and human beta-defensin 2 in a time-dependent fashion, while the cells infected with heat-killed bacteria did not show a significant production either of the cytokines or beta-defensin 2 at any time. In conclusion, we demonstrate the correlation between multiplication of C. pneumoniae in human gingival fibroblasts and release of interleukin-6, interleukin-10 and up-regulation of beta-defensin 2, suggesting that gingival fibroblasts may be a periodontium niche for obligate intracellular C. pneumoniae and may play a role in innate gingival immune system and inflammatory response mechanisms of periodontitis.